class BollingerBandsStrategy(Strategy):
 n = 40 # Period for Bollinger Bands
 k = 2 # Number of standard deviations
 def init(self):
 # Compute Bollinger Bands using talib
 self.upper_band, self.middle_band, self.lower_band = self.I(
 tb.BBANDS, self.data['Adj Close'], timeperiod=self.n, nbdevup=self.k, nbdevdn=self.k
 )
 
 def next(self):
 if len(self.data) < self.n:
 return # Not enough data to make a decision
 close = self.data['Adj Close'][-1]
 prev_close = self.data['Adj Close'][-2]
 upper = self.upper_band[-2]
 lower = self.lower_band[-2]
 if not self.position:
 # Buy signal: previous close crosses above the previous lower Bollinger Band
 if prev_close < lower and close > lower:
 self.buy()
 else:
 # Sell signal: previous close crosses below the previous upper Bollinger Band
 if prev_close > upper and close < upper:
 self.position.close()